Slide potentiometer

ABSTRACT

A pair of substantially identical body halves are jointed face to face to leave a slot in one surface for a slider. One or both body halves have a resistive track and a collector track including a center terminal. The slider has sliding contacts to connect the resistive track and collector track. A dust shield is mounted so as to be stationary in the body to prevent ingress of dust through the slot. The slider has cooperating body parts on either side of the dust shield so as to be slidable without moving the dust shield.

United States Patent Howitt 5] July 11, 1972 54] SLIDE POTENTIOMETER3,151,307 9/1964 ..,.338/164 x 3,362,004 1/1968 Bang 1 ..338/183 [72]c'lammgan Soulh 3,510,821 5/1970 Eberwein et a1. ..338/184 x [73]Assignee: A.B. Electronic Components Limited, primary Examine, ewiSMyers Glamoljgan, South wales Assistant Examiner-U. Weldon 22 Filed; 0(20 97 Attorney-Merrill F. Steward et a1.

21 Appl. No.: 190,805 [57] ABSTRACT A pair of substantially identicalbody halves are jointed face to [52] U.S.Cl. ..338/183, 338/184, 338/199face to leave a slot in one surface for a slider. One or both bodyhalves have a resistive track and a collector track includ- [58] FieldofSearch ..338/1l8, 160, 161, 176, 183, ing a center terminal. Theslider has sliding contacts to con- 338/ 184, 194, 198, 199, 131 nectthe resistive track and collector track. A dust shield is mounted so asto be stationary in the body to prevent ingress References Cited of dustthrough the slot. The slider has cooperating body parts UNITED STATESPATENTS on either side of the dust shield so as to be slidable withoutmoving the dust shield.

6 Claim, 12 Drawing Figures SLIDE POTENTIOMETER This invention relatesto improvements in slide potentiometers of the type including aresistive track, a collector track including a center terminal, a sliderhaving sliding contacts to connect the resistive track to the collectortrack, and a dust shield to prevent ingress of dust through a slot inthe body through which the slider projects.

The bodies of such potentiometers are generally made from twosubstantially identical halves joined face to face to leave a slot inone surface of the body. The halves have cooperating formations,generally pins and holes to locate the parts together. Each half of thebody may in fact have an individual resistive track and collector trackand the slider may carry a movable contact assembly at each side wherebytwo potentiometers are ganged together.

Accordingly to the present invention, the dust shield is mounted so asto be stationary in the body, and the slider has cooperating body partson either side of the dust shield.

In addition, the body halves may have some or all of the followinguseful constructional features:

a. The cooperating formations between the body halves include a pin anda hole located near the center of the body and these holes are ofstepped bore to provide easy location and a force fit, the steppingbeing preferably achieved by including a number of flats in the wall ofthe bore starting at half depth;

b. A recess for the collector track is formed with pips to provide snapretention of the collector track;

0. A recess for the resistive track has formations for snap retention ofthe resistive track to hold it in position during assembly and also toaugment the heat securing of the ends;

d. Notches on the slotted surface of the body are provided toaccommodate optional pressure plates to define any of a variety ofindent positions if required;

e. Arrangement of non-handed hole and pin pairs on the outer walls ofthe body halves for interconnection of other bodies by means of adjacentholes or attachment of side screens, so that the body halves areidentical in this respect;

f. Tee slots are provided for accommodation of the ends of a screenbetween the two potentiometers in the identical body halves; and

g. A plurality of recesses, e.g., seven in number, are provided foraccommodating the center terminal at various positions along thecollector track.

The invention will be further described with reference to theaccompanying drawings, which show a preferred form of slidepotentiometer according to the present invention, in which:

FIG. 1 is an elevation of the inside of a body half;

FIG. 2 is a bottom plan view thereof;

FIG. 3 is an elevation of the outside thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is an enlarged view of a part of FIG. 1;

FIG. 6 is a section on the line VI-VI of FIG. 5;

FIG. 7 is a section on the line VII-VII of FIG. 1;

FIG. 8 is a section on the line VIIIVIII of FIG. 1;

FIG. 9 is an enlarged transverse section through the slider and dustshield;

FIG. 10 is an enlarged elevation of the slider;

FIG. 11 is an elevation of one half of the potentiometer;

FIG. 12 is an enlarged elevation of a modified slider.

The body half illustrated in FIGS. 1 to 8 of the drawings comprises anupper wall 1 having a half slot 2 formed in its inner surface facing thecomplementary body half so as to define a slot through which a slider 26(described hereafter with reference to FIG. 9 and 10), will project foroperation from outside the body. The body half also has a lower wall 3,end portions 4 and 5 and a side wall 6, the outer surface of which isillustrated in FIG. 3 and the inner surface in FIG. 1.

The two body halves are located together by engagement of a pin 7 on theend portion 5 within a recess 8 on the end portion 4 when two similarhalves are brought together. In addition, there is provision of a pin 9and a recess 10 close to the center of the body along the bottom wall 3,and the pin 9 is arranged to be a force fit in the matching recess onits adjacent half. FIGS. 5 and 6 illustrate that the recess is of adiameter slightly greater than that of the pin 9 to about half its depthso that location is fairly simple, and is then provided with threeflatted zones 10a, which effectively reduce the diameter of the recess10 so that entry of the pin 9 beyond the half-way point is achievedagainst resistance, and results in a force fit.

A housing for a collector track (not shown) with a center terminal atone of seven positions is formed between a continuous rib 11 and abroken rib 12 standing up from the wall 6.

Along these upstanding ribs, there are provided inwardly pointing pips13 (see along FIG. 8) which provide a snap fit for retention of thecollector track in the housing or recess formed between the ribs 11 and12. It will also be seen that the breaks in the rib 12 are associatedwith shallow recesses 14 to enable the center terminal integral with thecollector track to pass beneath the resistive track houses on theopposite side of the rib l2, and pass out through a selected one of theapertures 15 provided at the junction of the wall 6 and the bottom wall3. Seven possible positions are thus provided for the center terminalalong the length of the potentiometer.

As previously mentioned, the resistive track is located on the oppositeside of the rib 12 from the collector track, and a pair of lugs 18 areprovided to locate it about the center tapping position, and afterassembly, pins 16 are heated or spun over to locate the track inposition. In order to assist retention of the track before, during andeven after this heat securing, there are provided on the rib 12 a pairof hook formations 17 (see also FIG. 7) under which the track can belocated.

Between the zone of the wall 1 having the slot 2, and the rib 11 thereis defined a track 19 which acts as a guide for the slider 26, and thisslider also runs around a dust shield 27 in the form of a strip which islooped round through track portions 20 formed in the end portions 4 and5. The ends of the shield 27 are secured simply by hooking aroundrespective abutments 21; other ways of securing the shield 27 can beenvisaged:

In cases where the two halves of the body each contain a separatepotentiometer, there may be a need to provide a screen or shield betweenthe two halves, and a pair of tee slots 22 are provided, one in each ofthe end portions 4 and 5, to anchor the ends of this screen or shield.The slider 26 has a recess 28 so that it can straddle this shield orscreen, and carries one set of moving contacts 29 on each side of it.

The slider 26 (FIGS. 9 and 10) has a body 30 having an integral flange31, which runs in the track 19 (FIG. 1). A plate 32, integral with ahandle 33 for moving the slider, is clipped into a recess in the flange31 and defines a slot through which the dust shield 27 passes. (Thisconstruction could be reversed, the handle having an integral flangerunning in the track 19, and the body having an integral plate clippedinto a recess in the flange.) On each side of the body 30, a contact 29is mounted which is in the form of a metal sheet from which twoprojection contact points 34, 35 have been punched out. The uppercontact point 34 is intended to engage the collector track, and thelower contact point 35 is intended to engage the resistive track and tocarry a carbon contact brush mounted in a hole 36.

Outside of the wall 6, there are provided a pair of holes 23, each ofwhich is associated with a pin 24, and these pins and holes are arrangedso that a similar, but reversed body half forming part of an adjacentbody can be mated with each half so that a bank of slide potentiometerscan be built up. In addition, these pairs of holes and pins serve forthe fixing of side screens, if these are required.

The top of wall 1 of the body half is also provided with a series ofnotches to accommodate optional pressure plates to define any of avariety of indent positions for the slider if these are required.Notches are illustrated at 25. Provision is also made for indentpositions internally by use of a hole 47 (FIG. 11) in the collectortrack into which the contact 34 indents. A variety of positions may bedefined in this way.

It is envisaged that the resistive element can be formed with a numberof extensions to form tapping positions, and any of these which are notused will be removed before the potentiometer is finally assembled. Thecenter tap position will normally be retained as it provides centrallocation of the element in the body between the lugs 18.

One half of the complete potentiometer assembly is shown in FIG. 11. Aresistive track 37 extends between the two pins 16; a terminal 38 isconnected to each end of the track 37 and extends out of the body. Acollector track 39 is housed between the continuous rib 11 and brokenrib 12. A center terminal 40 at the side of the collector track 39extends through rib 12, passes under the resistive track 37, from whichit is separated by an insulating strip 41, if required, and extends fromthe body.

The slider 26 slides around the dust shield 27. The contact points 34,35 which are visible in FIG. 11 are those which engage the collectortrack, and resistive track respectively, of the other body half, thecontact point 35 having a carbon contact brush 42. The twopotentiometers housed in the body are shielded from each other by astrip 43 the ends of which are anchored in the tee slots 22; the strip43 passes through the recess 28 (FIG. 9) in the slider 26.

Various modifications may be made within the scope of the invention. Forinstance slider 26 can have an alternative metal contact 44 (FIG. 12) inwhich three legs have been punched out, the upper leg 45 being intendedto engage with the collector track and the lower pair of legs 46 beingintended to engage with the resistive track.

lclaim:

1. In a slide potentiometer comprising a body consisting of a pair ofsubstantially identical body halves, each body half having a recesscooperating with the corresponding recess in the other body half to forma longitudinal slot, a slider projecting from the body through the saidslot, at least one of the said body halves housing a resistive track anda collector track, the said collector track having a terminal, slidingcontacts on slider for electrically connecting the resistive track tothe collector track, and a dust shield for preventing ingress of dustthrough the said slot, the improvement that the duct shield is mountedto be stationary in the body and that the slide comprises cooperatingbody parts located on each side of the dust shield to define a throughway whereby the slides may be moved along the slot without disturbingthe dust shield.

2. A slide potentiometer as set forth in claim 1, in which the bodyportions are joined by cooperating formations including a pin and holeconnection near the mid point of the body, the

hole being of stepped bore to provide ease of locations and a 3. A slidepotentiometer as set forth in claim 2, in-which the bore of the hole isprovided with a plurality of flatted areas from above half depth to thebottom of the hole.

4. A slide potentiometer as set forth in claim 1, comprising unitaryribs in the body half to define a recess for the collector track, thesaid ribs being formed with snap retention pips for holding thecollector track in position.

5. A slide potentiometer as set forth in claim 1, comprising formationsdefining a recess for the resistor track, locating pins for securing theends of the resistor track and snap retention means on at least one ofthe said formations intermediate the ends of the recess for retainingthe resistive track in position.

6. A slide potentiometer as set forth in claim 1, in which at least oneof said body halves has a plurality of spaced recesses for accommodatingthe center terminal of the collector track at any one of a plurality ofspaced positions.

1. In a slide potentiometer comprising a body consisting of a pair ofsubstantially identical body halves, each body half having a recesscooperating with the corresponding recess in the other body half to forma longitudinal slot, a slider projecting from the body through the saidslot, at least one of the said body halves housing a resistive track anda collector track, the said collector track having a terminal, slidingcontacts on slider for electrically connecting the resistive track tothe collector track, and a dust shield for preventing ingress of dustthrough the said slot, the improvement that the duct shield is mountedto be stationary in the body and that the slide comprises cooperatingbody parts located on each side of the dust shield to define a throughway whereby tHe slides may be moved along the slot without disturbingthe dust shield.
 2. A slide potentiometer as set forth in claim 1, inwhich the body portions are joined by cooperating formations including apin and hole connection near the mid point of the body, the hole beingof stepped bore to provide ease of locations and a firm fit.
 3. A slidepotentiometer as set forth in claim 2, in which the bore of the hole isprovided with a plurality of flatted areas from above half depth to thebottom of the hole.
 4. A slide potentiometer as set forth in claim 1,comprising unitary ribs in the body half to define a recess for thecollector track, the said ribs being formed with snap retention pips forholding the collector track in position.
 5. A slide potentiometer as setforth in claim 1, comprising formations defining a recess for theresistor track, locating pins for securing the ends of the resistortrack and snap retention means on at least one of the said formationsintermediate the ends of the recess for retaining the resistive track inposition.
 6. A slide potentiometer as set forth in claim 1, in which atleast one of said body halves has a plurality of spaced recesses foraccommodating the center terminal of the collector track at any one of aplurality of spaced positions.